Tag Archives: Micro

Tiny, Pocket, Micro Wood Burning Stove

This is an article to discuss my building of a tiny wood stove, also referred to as a pocket stove or micro stove.

After doing some research on heating my small workshop, and subsequently being led to Google results that showcased tiny homes with tiny wood stoves, I thought, “what the hell!” I could build something that would heat the shop. Thus my quest began…

I got a piece of 6 1/2″ id (inside diameter pipe, 1/4″ wall thickness, from the scrap pile at work. It was rough cut to about 10″ long.

As a side note, on my way out of work, I did get a few odd looks and one comment about “burning twigs.” I kindly notified this jokester that I would be burning regular wood. And that I would be building a tiny wood splitter to get them down to size.

A metal cutting band saw is a must!
A metal cutting band saw is a must!

A metal cutting bandsaw cut the ends cleanly and squarely.

4" c-channel base tacked on.
C-Channel tacked into place for the base.

 

 

 

I took the pipe and welded on some c-channel I had laying around. This created a fairly stable base. Although I will need some legs to get it off the ground. Maybe some 4″ x 1″ tubing will do the trick?

 

Plasma cutter makes quick work of the smoke stack hole.
Plasma cutter makes quick work of the smoke stack hole.

Next I used the plasma cutter and added a piece of 4″ pipe for the chimney. This I will connect to 4″ stove pipe and vent to the outside. Duh.

 

 

Precision placement of the smoke stack. :)
Precision placement of the smoke stack. 🙂

I will also build a little damper that will go here to control air flow. I found that this is very necessary to achieve the maximum burn. Air flow is key. UPDATE: No damper necessary. You’ll see why below.)

 

 

 

 

Smoke stack welded in place.
Smoke stack welded in place.

I welded the pipe into place and then ground the welds down for a smoother look. Grinding also covers any imperfections in my welds, of which I had a few.

 

 

 

 

Back side of stove covered.
Back side of stove covered.

Again, I used the plasma cutter to make the back wall that was welded into place.

 

 

 

 

 

Hinge bolted and a large nail I bent into a handle.
Hinge bolted and a large nail I bent into a handle.

And now, the front door. Single hinge and a large nail I had laying around for the handle. For reference, the nail is a timber nail and is about 8″ long.

Thank you to my son Andrew for helping design the hinge. He’s got potential to be a great craftsman!

Ready for testing. outside of course.
Ready for testing. outside of course.

It now has the basic shape of a wood stove. Not nearly done, but close enough for testing.

 

 

 

 

 

Twigs to get started with.
Twigs to get started with.

Time for a trial run. Let’s light this candle! Twigs and scrap wood from the shop. It started slowly and then…

 

 

 

 

 

Let's throw in some scrap wood from the workshop.
Let’s throw in some scrap wood from the workshop.

…this bad boy is burning hot! Well, not really HOT, hot.

It needs to be around 300-500 Fahrenheit. right now it burns at around 200. But it’s got potential, I think.

 

 

 

 

Too much draft! I had to think quickly and cover the chimney a little over half way. (UPDATE: The reason for the chimney cover is that I didn't have enough air flow into the stove. It was burning itself out. I now have plenty of air flowing in and no damper required.)
Too much draft! I had to think quickly and cover the chimney a little over half way. (UPDATE: The reason for the chimney cover is that I didn’t have enough air flow into the stove. It was burning itself out. I now have plenty of air flowing in and no damper required.)

Primary Air Flow:
It’s still missing a damper and an adjustable air inlet for the draft which will allow me to fine-tune the fire. I will install those tonight and will post more pics. (UPDATE: No damper needed after some testing and research. Thanks Google. What this thing needs is the free flow of air in and out. Damper that I ended up installing has now been removed.)

Secondary Burn:
Another option I am considering is an air injection nozzle.  By injecting air into the fire it will burn super hot and more cleanly. I need to research this a little more. (UPDATE: This works well. See pics below. I have secondary air being drawn in through black iron pipe into the back of the stove. The air is warmed and flows into the stove at the top of the burn chamber so that it can help ignite the gases which should help it burn cleaner.)

Everything burning as expected.
Everything burning as expected.

OK, so I’ve done a lot more research and made some modifications. Forget the damper! It’s unnecessary if I build this right. I need good airflow. The fire will create the right draft as long as I have a way for air to be drawn in.

I also need secondary air to mix with the gases at the top of the burn chamber for clean burning.

Cut holes in bottom of burn chamber to allow air to be drawn in

Here are the holes I added to allow air to be drawn up into the fire from below. This made a huge difference in how well the fire burned. I was also able to keep a good burn going with the door completely closed, which was a requirement.

 

 

 

Secondary air tube to bring warm air into the gases at the top of the burn chamber

Here you can see the secondary air inlet that I made out of some black iron pipe. I drilled holes into it and welded one end closed. It comes in through the back of the stove and will draw in fresh air that will be heated as it enters. Then it will mix with the gases from the fire and ignite them to burn everything more cleanly.  I’ve researched this as much as possible and this is the design I came up with. I am sure there are better ways to do it but this way was fairly straight forward and easy to change if necessary.

Inside view

I also added a little grate to keep the wood up off the floor. This allows unobstructed airflow into the burn chamber. I am contemplating making it slightly narrower though so that the wood can sit a little lower and will allow for more to be burned at a time.

 

 

Added stove pipe to test burn

I purchased a 24″ flue pipe at the local heat and air store. I am just using this for testing. It made a big difference on the air flow because it kept the wind from causing back drafts into the stove. These back drafts would cool the stove too much and caused smoke to come bellowing out. With the draft up this pipe I got a clean burn with almost zero smoke coming out and temperatures in the stove we almost 100 degrees higher than they were during the initial trial run.

Burning hotter!

I am now getting temperature readings in the “Burn Zone.” Before, I had temps in the “Creosote Zone” and everything was smokey. We are getting closer to a fully functional unit. I would like it to go up about another 50-100 degrees before I call it a complete success though.

Fire is glowing

 

 

Now it looks like a stove
Side view shows intake for secondary air and flat top

Time to finish it up, for now. Needs a little flat area on top, to heat my coffee, and some black stove paint. Don’t want it looking like something from the Sanford and Son yard.

 

 

 

 

Here she is! All dolled up and ready for the prom. Notice that I welded the air inlet plate on? No need to close off the air source. I also added an additional hole in it to allow for sufficient air flow into the stove.

Also, check out the little platform I welded to the top of the stove. This gives it a nice flat area for setting my coffee cup to keep it warm.

From this angle you can see the inlet for the secondary air. I extended it out from the back of the stove about 3″ so that it had plenty of time to heat the air before mixing with the gases. Hot air is what you want mixing with the gases. When this ignites it burns very clean.

I also left the threaded end on the pipe so that I could force air in if required. I might go ahead and add a small fan, or connect it to my air compressor, to force the air into the burn chamber to see if it makes any difference. I will update this post with the results.

UPDATED!!!

Injecting air from compressor into burn chamber.
Injecting air from compressor into burn chamber.

I fit a connector and ball valve to the secondary burn inlet. This way I could port a direct stream of air from my air compressor into the burn chamber. It seemed to burn correctly. Very clean with almost no smoke. And it looked like it was burning very hot. When I put the thermometer over the top of the vent pipe it quickly went over 600 degrees before my hand was too hot and I had to drop the thermometer.

The flue is melting!
The flue is melting!

So the guy at the hardware store was right when he said I really shouldn’t use the gas flue pipe for a wood stove. Turns out my stove burns pretty hot and melted the test flue pipe I was using.

I guess this flue wasn't up to the task.
I guess this flue wasn’t up to the task.

I need to either build mine from 4″ steel pipe or spend the money on actual flue pipe for a wood stove which is pretty expensive. I’m cheap so I will probably just find some steel pipe at the recycling yard.

UPDATE!

I finally got around to putting on a proper flu pipe and it made a huge difference in the way the stove functions. 

I also found that cutting firewood to the appropriate size for this tiny stove made a difference too.

 

 

 

 

 

This fire burns really hot now. This stove will be perfect to take camping.

Hot fire!